1. Field of Invention
The invention relates to an illuminating technology. More particularly, the invention relates to an illuminating apparatus using a light guide plate.
2. Description of Related Art
There are so many designs of an illuminating apparatus seen in the conventional art. However, depending on the purpose of a light source being involved, the different concerns are made. For the considering a light source with large area in better uniformity of light intensity is concerned in various applications. Particularly, for the back light module used in flat image display, the light intensity is required to be uniform at a large area. However, the uniform light is rather monotone, and could not produce pleasant visual effect.
FIG. 1 is a drawing, schematically illustrating perspective view of a conventional back light module. In FIG. 1, as disclosed in U.S. Publication 2007/0171678, the back light module is formed by a light guiding unit. The light guiding unit of a direct illumination type backlight assembly guides light generated from a point light source arranged on a direct illumination portion of a display panel toward the display panel. The light guiding unit has a substantially plate shape including a recessed portion 15 that is recessed toward the point light source and a protruding portion 30 that is protruded toward the point light source. The protruded portion 30 may have substantially the same profile as the recessed portion 15. The protruded portion 30 has a light incident surface to receive the point light source, so as to convert into the plane light.
FIG. 2 is a drawing, schematically illustrating a cross-section view of a conventional illuminating apparatus. In FIG. 2, as disclosed in U.S. Publication 2003/0128957, a light guide panel 40 is used to produce a planar light in an area with uniform light intensity. The light source is incident into the light guide panel 40 from the incident surface 42 at the tubular structure 44. In other words, the light guide panel 40 uses the tubular structure 44 to convert the incident point-like light source into a planar light in large area with uniform light intensity.
FIG. 3 is a drawing, schematically illustrating a cross-section view of a conventional illuminating apparatus. In FIG. 3, as disclosed in U.S. Pat. No. 6,356,394, a mushroom-shaped light guide for a homogeneous illumination of a circular scale of a motor vehicle operating device is disclosed. A light source, for example, a light emitting diode (LED) 52 is arranged opposite a light input surface of the mushroom-shaped cone 50. The mushroom-shaped cone 50 has a recess portion 54. As shown the light path, a light beam generated by the light source 52 is guided in the mushroom-shaped cone 50 and exits at the side edge with rather parallel light beam, which may be deflected by a prism into the forward direction at the peripheral region.
In the foregoing conventional designs of the illuminating apparatus, the output light is intended to be uniform in a large area or to have a rather parallel light beam.